这个DNS系列现在有以下几篇文章
DNS EDNS DNSSEC DNS over HTTPS 完整代码请看DNS

EDNS

上一篇我们写了DNS,EDNS就是DNS的功能扩充.
上一篇的DNS里头部有ARCOUNT的计数,EDNS就包含在那个里面,EDNS发送的请求在请求头之后的Additional中,应答在Answer和Authoritative之后,我们可看以下图,跟清晰了吧

    +---------------------+    |        Header       |    +---------------------+    |       Question      | the question for the name server    +---------------------+    |        Answer       | RRs answering the question    +---------------------+    |      Authority      | RRs pointing toward an authority    +---------------------+    |      Additional     | RRs holding additional information    +---------------------+

协议格式

具体协议内容请看rfc2671,rfc7871